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Made available in DSpace on 2021-06-25T12:40:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01. Added 1 bitstream(s) on 2021-07-15T14:36:37Z : No. of bitstreams: 1 S0100-40422021000100064.pdf: 351814 bytes, checksum: 4cae0f233c7cc9ac074ed30bb30901cd (MD5) This study compares the techniques cold vapour atomic fluorescence spectrometry (CV-AFS) and inductively coupled plasma mass spectrometry (ICP-MS) for the determination of Hg in biological samples (hepatic tissue from marine tetrapods). Acid digestions were performed for the samples and aliquots of them were analysed by ICP-MS and CV-AFS. To minimize the Hg memory effect in its determination by ICP-MS, gold (200 mu g L-1 in 5% v v(-1) HCl) was added to the sample digests. The detection limits were 0.02 mg kg(-1) for ICP-MS and 0.01 mg kg(-1) for CV-AFS. Accuracy was assessed by the calculation of the recovery obtained from TORT-3 (lobster hepatopancreas) certified reference material analysis. Accurate results were obtained for both CV-AFS and ICP-MS. The comparison of the results obtained for hepatic tissue with and without lyophilization showed a significant difference among them (at 95% of confidence level), evidencing losses of Hg in the lyophilization process. Univ Estadual Paulista, Ctr Estudos Ambientais, BR-13506900 Rio Claro, SP, Brazil Univ Fed Amazonas, Dept Quim, BR-69067005 Manaus, Amazonas, Brazil Inst Nacl de Pesquisas da Amazonia, BR-69060001 Manaus, Amazonas, Brazil Univ Estadual Paulista, Ctr Estudos Ambientais, BR-13506900 Rio Claro, SP, Brazil

The Amazon is a region known worldwide for its biodiversity, but also has high mercury levels in various compartments of the environment. In this work, Hg was determined in sediment of Educandos Basin, one of the most populated regions of Manaus (AM), in order to establish the surface distribution of the contaminant in coarse and fine fractions. Surface sediment samples were collected in nine locations in the basin; three sources of the main stream and the rest in areas contaminated by human activity. Mercury concentrations were determined in raw samples (total fraction) and dried

The developed method in this work is defined as a chemical method of indirect quantification of the reducing capacity of vegetable extracts. It is based on the reduction of ions Fe3+ by chemical substances contained in the extracts and subsequent quantification of Fe2+ ions for spectrophotometric technique in range of the visible using the adapted method of the reagent 1,10-phenanthroline. The procedure of the development and validation was composed by three parts: characterization of the quantification of Fe2+ in the form of the complex [Fe(fen)3]2+; reduction of ions Fe3+ by organic compounds and vegetable extracts; and characterization of the proposed method. Ascorbic acid, hydroquinone, catechol, pirogallol, quercetine, Trolox™, BHA, BHT, cisteine and glutathione were used as reference reducing. The samples of dry vegetable extract were obtained from bank of extracts of the Laboratory of Bioprospection and Biotechnology, installed in the Coordenação de Pesquisas de Produtos Naturais (CPPN) of the Instituto Nacional de Pesquisas da Amazônia (INPA). The criterion for the choice of the extracts used in the validation process was based on measures (peaks or oxidation bands) by cyclic voltammetry technique. The compound [Fe(fen)3]2+ is stable and in the tested conditions it did present maximum absorption in 508.8 nm with molar absorptivity around (1.084 ± 0.003) × 104 L.mol-1.cm-1. The quantification of ions Fe2+ in the form of the compound [Fe(fen)3)]2+ is linear in the range from 0.2 to 10.0 g.mL-1. The adjusted line obtained by the method of minimum squares presented equation ABS = 0.01444 ± 0.19417 × [Fe2+] (R2 = 0.9994) for concentrations up to 10.0 g.mL-1 and ABS = 0.00263 ± 0.19974 × [Fe2+] (R2 = 0.9997) up to 5.5 g.mL-1. Established oxidation process consists of two stages: (1) reaction with ions Fe3+ and (2) reaction with ions Fe3+ in the presence of 1,10-phenanthroline. The oxidation degree and the linearity vary in agreement with the reaction mechanism. The proposed method presented positive answer for the glutathione, differently of other methods described in the literature. The developed method and validated presents the following characteristics: Limit of decision, of detection and of quantification was of 0.17 g Fe2+.mL-1 , 0.20 g Fe2+.mL-1 and 0.31 g Fe2+.mL-1, respectively; Reproducibility and repeatability between 0.5% and 3.9%; absolute discrepancy between 1.3% and 3.9% for the following reducing: ascorbic acid, hydroquinone and BHA. Ethanol, methanol, acetone and DMSO can be used to dissolve the vegetable extracts. Ethylene glycol and DMF can be used, but they can coordinate with Fe2+/Fe3+ ions. The coordination of the Fe2+/Fe3+ ions for ligands present in the extract are labile in relation to chelante 1,10-phenanthroline. The Co2+, Cu2+, Ni2+, Mn2+, Sn2+, Zn2+, Mg2+, Ca2+, Na+, K+, NH4+, SO42-, Cl- e NO3don't interfere in the quantification of the complex [Fe(fen)3]2+, but PO43- ion interfere in higher concentrations than 10 g Fe2+.mL-1. The UV radiation produces false positive, converting Fe3+ in Fe2+. With base in the obtained results, it can be concluded that the method developed for quantification of the reducing capacity of vegetable extracts was appropriate and of easy execution. O método desenvolvido nesta dissertação é definido como um método químico de quantificação indireta da capacidade redutora de extratos vegetais. Baseia-se na redução de íons Fe3+ por substâncias químicas contidas nos extratos e posterior quantificação de íons Fe2+ por técnica espectrofotométrica na região do visível usando o método adaptado do reagente 1,10-fenantrolina. A metodologia de desenvolvimento e validação adotada foi composta por três partes: caracterização da quantificação de íons Fe2+ na forma do complexo [Fe(fen)3]2+; redução de íons Fe3+ por substâncias orgânicas e extratos vegetais; e caracterização do método proposto. Ácido ascórbico, hidroquinona, catecol, pirogalol, quercetina, Trolox®, BHA, BHT, cisteína e glutationa foram usados como redutores de referência. As amostras de extratos vegetais secos foram obtidas do banco de extratos do Laboratório de Bioprospecção e Biotecnologia, instalado na Coordenação de Pesquisas em Produtos Naturais (CPPN) do Instituto Nacional de Pesquisas da Amazônia (INPA). O critério para a escolha dos extratos usados no processo de validação foi baseado em medidas (picos ou bandas de oxidação) por técnica de voltametria cíclica. O complexo [Fe(fen)3]2+ é estável e nas condições testadas apresentou absorção máxima em 508,8 nm com absortividade molar em torno de (1,084 ± 0,003) × 104 L.mol-1.cm-1. A quantificação de íons Fe2+ na forma do complexo [Fe(fen)3)]2+ é linear na faixa de 0,2 a 10,0 g.mL-1. A reta ajustada obtida pelo método dos mínimos quadrados apresentou equação ABS = 0,01444 ± 0,19417 × [Fe2+] (R2 = 0,9994) para concentrações até 10,0 g.mL-1 e ABS = 0,00263 ± 0,19974 × [Fe2+] (R2 = 0,9997) até 5,5 g.mL-1. O processo de oxidação estabelecido consiste em duas etapas: (1) reação com íons Fe3+ e (2) reação com íons Fe3+ na presença de 1,10-fenantrolina. O grau de oxidação e a linearidade variam de acordo com o mecanismo de reação. O método proposto apresentou resposta positiva para o peptídeo glutationa, diferentemente de outros métodos descritos na literatura. O método desenvolvido e validado apresenta as seguintes características: Limite de decisão, de detecção e de quantificação iguais a 0,17 g Fe2+.mL-1, 0,20 g Fe2+.mL1 e 0,31 g Fe2+.mL-1, respectivamente; Reprodutibilidade e repetibilidade entre 0,5% e 3,9%; Discrepância absoluta entre 1,3% e 3,9% para os seguintes redutores ácido ascórbico, hidroquinona e BHA. Etanol, metanol, acetona e DMSO podem ser usados para dissolver os extratos vegetais. Etilenoglicol e DMF podem ser usados, mas podem coordenar com íons Fe2+/Fe3+. A coordenação dos íons Fe2+/Fe3+ por ligantes presentes no extrato é lábel em relação ao quelante 1,10-fenantrolina. Os íons Co2+, Cu2+, Ni2+, Mn2+, Sn2+, Zn2+, Mg2+, Ca2+, Na+, K+, NH4+, SO42-, Cl- e NO3não interferem na quantificação do complexo [Fe(fen)3]2+, mas o íon PO43- interfere em concentrações maiores que 10 g.mL-1. A radiação UV produz um falso positivo, convertendo Fe3+ em Fe2+. Com base nos resultados obtidos, pode-se concluir que o método desenvolvido para quantificação da capacidade redutora de extratos vegetais mostrou-se adequado e de fácil execução.